1. Field of the Invention
This invention pertains to a new and improved apparatus and process for the production of a hollow workpiece being profiled, preferably at least internally, in a straight or helical manner relative to the workpiece axis via cold forming.
According to the invention, workpieces are produced that have profiling on their inside and/or the outside surfaces.
When profiling is produced on both the inside and outside surfaces more or less close similarity or far reaching differences between the inner and outer profile can be produced.
In terms of the profiles per se, the gearing or toothing being produced, for example, can be fabricated either as a splin or a gear.
2. Background of the Invention
For the production of quality precision profiles, for example, gearing or toothing, relative to hollow workpieces the well know Grob method is outstanding. This method will be summarized hereinafter even though in this particular technology or art, both from documentation as well as from actual practice, it is of world renown and no further explanation is needed for those skilled in this art.
For example, the special development of the Grob method which permits the fabrication of an outer toothing or gearing in a relatively thick-walled hollow workpiece is disclosed in Swiss Patent No. 579,427, in French Patent No. 7,538,539 and in German Patent No. 25 49 230, to which reference may be readily had and the disclosures of which are incorporated herein by reference. With these methods, different toothings or gear tooth systems can be fabricated on the inside and the outside of the workpiece.
In a relatively thin-walled hollow workpiece, the Grob method of impact roll-shaping permits fabrication via cold forming or cold working to simultaneously produce an outer profile and an inner profile, whose profiles may differ. For this, the tubular portion of the raw or unfinished workpiece is mounted on a specific mandrel or holder whose external toothing or teeth correspond to the internal toothing or teeth of the workpiece which is to be fabricated. The workpiece in this setup is infed or advanced along its workpiece axis and turned or rotated relative thereto. During this workpiece feed, the workpiece is externally worked by annular or ring-like profiled forming rolls or rolling tools, whereby each forming roll or rolling tool performs single or individual blow-like or impact-forming operations in rapid succession in coupled sequence in the direction of the advance of the workpiece. The single or individual blow-like impact or forming operations are consecutively carried out by the same forming roll or rolling tool in a screw-like or helical zone determined by the infeed of the workpiece. The consecutively following single forming processes, in the direction of the profile, within the same tooth spacing, are accomplished as operations on the workpiece in a partially overlapping manner. In the process of cold forming on the profiled mandrel during each single blow-like or impact-forming operation, material is pushed along a relatively small section of the workpiece into the depressions of the mandrel, namely flowing mainly in a radial direction.
With relatively thick-walled workpieces, inner profiles can only be produced via the use of a profiled mandrel. If the form or shape of the outer surface is not of great consequence, it can be finished more or less smooth or even. Rolling heads or forming tools without any profiling may be utilized since they do not have to be exactly synchronized with reference to the rotation of the workpiece.
In the prior state of technical development the substantially dished or pot-shaped hollow bodies have been produced on very expensive step or transfer presses in multiple steps. It is only after the last pressing step that the unfinished or hollow bodies can be transferred to Grob machines and mounted on mandrels or holders thereon and be subsequently finished or further worked upon via the Grob method.